cream of leek and potato soup with parsley mushrooms

Lindsey Bareham

Making thick, smooth soups with an over-generous garnish has become my favourite way of using up leftovers. Here a lemony, tarragon-flecked pale green soup is finished with finely-sliced mushrooms that have been quickly stir-fried in butter with parsley. Torn leftover chicken is another good addition.

serves 4, prep 20 min, cook 25 min

1 onion
500g trimmed leeks
50g butter
1 tbsp vegetable oil
150g potato
5g tarragon
25g flat leaf parsley
1 lemon
1 chicken or vegetable stock cube
200g closed cup mushrooms

Halve, peel and finely chop the onion. Melt half the butter in half the oil in a spacious, lidded pan over a medium heat. Stir in the onion and cook, stirring often, for about 10 min until soft but hardly coloured. Meanwhile, slice the leeks thinly, agitate in a bowl of water and drain. Stir the leeks into the onion with a generous pinch of salt. Cover and cook, stirring once, for 10 min until sloppy and soft.

Meanwhile, peel, dice and rinse the potato. Strip the tarragon from the stalk and chop the leaves. Finely chop the parsley leaves. Dissolve the stock cubes in 900ml boiling water. Add potato and stock to the pot. Simmer briskly, partially covered, for 10 min or until the potatoes are soft. Add tarragon and blitz smooth in batches. Return to a clean pan. Reheat and season to taste with lemon juice and salt. Wipe the mushrooms, slice thinly and melt remaining butter in remaining oil in a frying pan. Stir in the mushrooms, stir-frying until moist and darkened. Stir in the parsley then tip into the soup.